Looking at the recent comScore statistic of video hosting sites, YouTube has now passed 100MM viewers per month and grabs 43% of the market. Not only is YouTube the dominant video publishing site on the Interent - it is also the dominant video search site.
Anyone looking for your brand or product on YouTube should find your channel and your videos over everybody else's. If that is not the case, you better go and fix it! Create a channel and upload some of your corporate videos, even if they are just copies of your TVCs.
This situation reminds me of the beginning of the Web, when not everybody had a Web page. YouTube is a repetition of that, just for videos only.
Your channel page is an additional piece of real estate through which you can communicate your message and which you can monetise. In addition, regard the YouTube channel as an advertising space for your other Web estates - in particular if you are a video content publisher.
For example, if people are looking for videos on the recent Victorian Bushfires, they would go to YouTube, where they find mostly poor quality user generated content. So, even if you have the best videos on the world about the Victorian Bushfires, people won't find them unless you make them aware of your content on YouTube und thus direct them to your Web estates.
Another important fact to note in this context is that videos - in particular YouTube videos - are 50 times more likely to appear on the first page of Google search results than any other Web content. This is another argument to support using YouTube videos as a means of SEO for your other content.